Field of the Invention
Embodiments of the invention herein generally relate to generating plasma in a substrate processing chamber.
Description of the Related Art
As the demand for larger flat panel displays and solar panels increases, so must the size of the substrate to be processed. For example, a large area substrate may exceed 2 square meters in surface area. To process these large area substrates, chamber size must also increase. For a plasma enhanced chemical vapor deposition (PECVD) chamber, the backing plate is naturally going to be at least as large as the large area substrate. Hence, in a PECVD apparatus for processing large area substrates, the backing plate may exceed 2 square meters in surface area. With an increase in backing plate size, an increase in RF current is sometimes necessary.
In PECVD, process gases may be introduced into the process chamber through a showerhead and ignited into a plasma by an RF current applied to the showerhead. As substrate sizes increase, the RF current applied to the showerhead may also correspondingly increase. A larger RF current increases the likelihood of arcing or parasitic plasma forming in undesired locations of the PECVD chamber. Arcing and parasitic plasma usurp RF current from the desired substrate process, making substrate processing more costly and less efficient.
Therefore, there is a need to control unwanted arcing and the formation of parasitic plasma.